The present invention relates to a mechanically-adjustable pitch propeller for marine vessels.
A propeller is designed by taking many parameters into account in order to provide the optimum thrust to the marine vessel provided therewith. For example, design parameters such as dimensions of the marine vessel body, load of the marine vessel, engine power, and density of the water the marine vessel cruises on are important inputs for determining the diameter and pitch of the propeller to be produced. Once a propeller has been produced with the blades thereof being static relative to the hub, the propeller may become heavy in torque against the cruise conditions if the pitch is large and it requires more power from the engine. However, if the pitch is low, i.e. if it is ‘light’, it cannot deliver enough engine power as thrust. In either case, performance of the propeller falls. A propeller designed with the blades being static relative to its hub (not adjustable pitch) is known as the ‘fixed pitch propeller’.
A new propeller needs to be used since modification attempts against the lightness of the propeller do not work. In the case where the propeller is heavy as term, the diameter can be downsized, however this brings along a number of problems (e.g. mass balancing problem of the propeller can take place due to the centrifugal force exerted, it can not be possible for each blade to uniformly face water). Such modification does not result in a propeller providing high performance in changing cruise condition, because when the conditions of the marine vessel changes, when the load thereof increases for instance, the performance of fixed pitch propeller falls again. For this reason, variable pitch type propellers have been proposed.
Use of variable pitch propellers against variable conditions such as marine vessel speed and load improves the performance (and therefore reduces fuel consumption). On the other hand, blades of the variable pitch propellers must be rotated by a certain amount relative to the blade hub so as to provide the optimum pitch by being controlled according to each changing condition. This often requires using a complex and costly control/drive mechanism.
Therefore, a propeller providing optimum thrust to a marine vessel according to the changed cruise conditions such as load and speed by adjusting the pitch in a simple and inexpensive way is needed.